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Re: Questions about HeapTupleHeaderData

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Questions about HeapTupleHeaderData
Date: 2008-08-21 14:15:36
Message-ID: 23238.1219328136@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM> writes:
> If I understand correctly then for read path (select) tuple is always 
> HeapTuple, because we need support select xmax ... And DatumTuple is 
> used for write path (insert/update) and it is "converted" to HeapTuple 
> in heap_insert/heap_update function.

No, DatumTuple is used for any free-standing composite-type Datum.
Thinking about it as "write path" and "read path" seems to me to
be missing the mark entirely.  In general most tuple-reading code
is supposed to work with either.

			regards, tom lane

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